linux-kernel - Re: [PATCH 3/3] mm: delete unused MMF_OOM

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Date:   Tue, 10 May 2022 09:10:45 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, Minchan Kim <minchan@...nel.org>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Christian Brauner <brauner@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Oleg Nesterov <oleg@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Jann Horn <jannh@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Peter Xu <peterx@...hat.com>,
        John Hubbard <jhubbard@...dia.com>, shuah@...nel.org,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, linux-kselftest@...r.kernel.org,
        kernel-team <kernel-team@...roid.com>
Subject: Re: [PATCH 3/3] mm: delete unused MMF_OOM_VICTIM flag

On Tue, May 10, 2022 at 8:51 AM Shuah Khan <skhan@...uxfoundation.org> wrote:
>
> On 5/9/22 9:00 PM, Suren Baghdasaryan wrote:
> > With the last usage of MMF_OOM_VICTIM in exit_mmap gone, this flag is
> > now unused and can be removed.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
> > ---
> >   include/linux/oom.h            | 9 ---------
> >   include/linux/sched/coredump.h | 1 -
> >   mm/oom_kill.c                  | 4 +---
> >   3 files changed, 1 insertion(+), 13 deletions(-)
> >
> > diff --git a/include/linux/oom.h b/include/linux/oom.h
> > index 6cdf0772dbae..25990e9d9e15 100644
> > --- a/include/linux/oom.h
> > +++ b/include/linux/oom.h
> > @@ -77,15 +77,6 @@ static inline bool tsk_is_oom_victim(struct task_struct * tsk)
> >       return tsk->signal->oom_mm;
> >   }
> >
> > -/*
> > - * Use this helper if tsk->mm != mm and the victim mm needs a special
> > - * handling. This is guaranteed to stay true after once set.
> > - */
> > -static inline bool mm_is_oom_victim(struct mm_struct *mm)
> > -{
> > -     return test_bit(MMF_OOM_VICTIM, &mm->flags);
> > -}
> > -
> >   /*
> >    * Checks whether a page fault on the given mm is still reliable.
> >    * This is no longer true if the oom reaper started to reap the
> > diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h
> > index 4d9e3a656875..746f6cb07a20 100644
> > --- a/include/linux/sched/coredump.h
> > +++ b/include/linux/sched/coredump.h
> > @@ -70,7 +70,6 @@ static inline int get_dumpable(struct mm_struct *mm)
> >   #define MMF_UNSTABLE                22      /* mm is unstable for copy_from_user */
> >   #define MMF_HUGE_ZERO_PAGE  23      /* mm has ever used the global huge zero page */
> >   #define MMF_DISABLE_THP             24      /* disable THP for all VMAs */
> > -#define MMF_OOM_VICTIM               25      /* mm is the oom victim */
> >   #define MMF_OOM_REAP_QUEUED 26      /* mm was queued for oom_reaper */
> >   #define MMF_MULTIPROCESS    27      /* mm is shared between processes */
> >   /*
> > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > index 36355b162727..11291b99599f 100644
> > --- a/mm/oom_kill.c
> > +++ b/mm/oom_kill.c
> > @@ -732,10 +732,8 @@ static void mark_oom_victim(struct task_struct *tsk)
> >               return;
> >
> >       /* oom_mm is bound to the signal struct life time. */
> > -     if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) {
> > +     if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
> >               mmgrab(tsk->signal->oom_mm);
> > -             set_bit(MMF_OOM_VICTIM, &mm->flags);
> > -     }
> >
> >       /*
> >        * Make sure that the task is woken up from uninterruptible sleep
> >
>
> Thank you for working on the new tests and cleanups.

Thanks for the review!

>
> This series needs a cover-letter that explains why this series is needed
> that includes the information from this last patch.
>
> Please send v2 with a proper cover letter starting with why this series
> is necessary. If you did that, it would have reviewers job is lot easier.
>
> Also it appears you are combining new tests with cleanup patches. I think
> patches 2/3 and 3/3 can be a separate series and the new test can be a
> separate patch.

I used the new selftest to test the patches but otherwise it's true,
they are unrelated. I was debating whether to send them separately and
with your blessing I'll split them up.
Thanks,
Suren.

>
> thanks,
> -- Shuah